Safety footwear and manufacture thereof

ABSTRACT

Disclosed are an article of safety footwear, a method of making the same, and a safety toe cap assembly adapted to be used in making such footwear. The article of safety footwear has a rigid, crush-resistant toe cap located in its toe region and having its outer surface bonded to the interior of the upper of the footwear article, a cushioning layer of resilient, compressible cellular (open-celled or closed cell or having both open and closed cells) cures elastomeric polymeric material, typically formed of opencelled cured cellular polyurethane, covering and being bonded to the inner surface of the toe cap, and a lining of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of the cushioning layer. The method of the invention is particularly characterized by the fact that it enables safety footwear to be manufactured at high production rates in marked contrast to conventional methods of making safety type footwear in which many hand fitting operations are normally involved.

United States Patent 1191 White 1451 Apr. 23, 1974 SAFETY FOOTWEAR ANDMANUFACTURE THEREOF Primary ExaminerAlfred R. Guest Attorney, Agent, orFirmRobert .1. Patterson [5 7] ABSTRACT Disclosed are an article ofsafety footwear, a method of making the same, and a safety toe capassembly adapted to be used in making such footwear. The article ofsafety footwear has a rigid, crush-resistant toe cap located in its toeregion and having its outer surface bonded to the interior of the upperof the foot-.

wear article, a cushioning layer of resilient, compressible cellular(open-celled or closed cell or having both open and closed cells) cureselastomeric polymeric material, typically formed of open-celled curedcellular polyurethane, covering and being bonded to the inner surface ofthe toe cap, and a lining of stretchable fabric having a low coefficientof friction covering and being bonded to the inner surface of thecushioning layer. The method of the invention is particularlycharacterized by the fact that it enables safety footwear to bemanufactured at high production rates in marked contrast to conventionalmethods of making safety type footwear in which many hand fittingoperations are normally involved.

12 Claims, 6 Drawing Figures SAFETY FOOTWEAR AND MANUFACTURE THEREOFBACKGROUND OF THE INVENTION United States Patents Baird, U.S. Pat. No.2,328,601, Sept. 7, 1943; Heckman, U.S. Pat. No. 2,426,211, Aug. 26,1947; Shultz, U.S. Pat. No. 2,795,868, June 18, 1957; Hunting et al.,U.S. Pat. No. 3,034,235, May 15, 1962;Rollman, U.S. Pat. No.3,165,841,.Ian 19, 1965.

Foreign Patents British, 722,803, (Dunlop), Feb. 2, 1955; French,

1,193,781, (Hutchinson), May 4, 1959; French, 1,260,816 (Latchere), Apr.14, 1961; French, 1,280,701, (Kleber-Colombes), Nov.'2l, 1961. Theforegoing patents, which are believed to be representative of the stateof the prior art, generally show safety shoes embodying metal toe capsincorporated in the toe area of the shoe. Some of them, such as Bairdand Kleber-Colombes, show cushioning elements of sponge rubber on theinside of the metal toe cap. It is fair to say that prior art practiceembodied a toe cap construction fabricated in situ using hand lay-upfabrication techniques designed to lock the toe cap into the article offootwear and involving many hand fitting operations. So far as thepresent inventor is aware, none has heretofore suggested a safety shoefabrication technique like that disclosed herein which makes it possibleto manufacture footwear having a safety toe cap of metal or other rigid,crush-resistant material, a cushioning layer on the interior of the capwhich provides comfort and thermal insulation, and a lining of smoothslippery fabric which provides protection against chafing of the footand facilitates donning and doffing and protects the cushioning layeragains abrasion, wear and other adverse influences, with a minimum ofseparate hand operations and in a manner adapting itself to highproduction rates.

SUMMARY OF THE INVENTION The invention has three principal aspects,namely a method of making safety footwear, a safety toe cap and liningassembly as an intermediate article of manufacture, and the resultingsafety footwear.

In its method aspects, the invention broadly comprises inserting intocontact and conformity with the toe region of the upper of an article offootwear a separately prepared safety toe cap and lining assemblycomprising a rigid, crush-resistant toe cap, a cushioning layer ofresilient, compressible cellular cured elastomeric polymeric material,typically open-celled cured polyurethane, covering and being bonded tothe inner surface of the metal toe cap, as by means of a solvent basedthermoplastic polyurethane adhesive of the type described more fullybelow, and a liner of stretchable fabric having a low coefficient offriction (so as to facilitate donning and doffing and prevent chafing ofthe toes) covering and being bonded in any suitable manner to the innersurface of the cushioning layer. The separately prepared safety toe capand lining assembly is caused to be adhered to the inner portion of thetoe of the article of footwear by means of an adhesive layer provided onthe outside of rigid crush-resistant toe cap. Preferably this adhesivelayer is formed on the outside of the toe cap prior to insertion of thetoe cap and lining assembly into position in the toe of the footwear andis laid down from a solvent-based thermoplastic polyurethane adhesive,the adhesive layer being allowed to dry to the point where it becomesextremely tacky but is no longer really wet. Upon insertion of theresulting assembly firmly into the toe of the boot or other footweararticle, the assembly becomes permanently bonded in position. Suchbonding is facilitated by having the footwear article heated to anelevated temperature prior to insertion of the toe cap and liningassembly.

The safety toe cap and lining assembly of the invention is anintermediate article of manufacture adapted to be incorporated in anarticle of footwear during manufacture thereof by simply inserting itinto the toe of the footwear article under appropriate conditionscausing permanentbonding of the outer surface of the rigid,crush-resistant toe cap to the inner surface of the toe portion. Thisassembly comprises a rigid toe cap, a coating of activatable adhesive,preferably deposited from a solvent-based thermoplastic polyurethaneadhe sive composition, on the outer surface of the cap, a cushioninglayer of resilient, compressible cellular cured polymeric material,especially open-celled polyurethane, covering and being bonded to theinner surface of the toe cap, and a liner of stretchable fabric having alow coefficient of friction covering and being bonded to the innersurface of the cushioning layer.

The construction of the safety footwear made according to the inventionwill be obvious from the descriptions herein of the method and of thetoe cap and lining assembly.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. Iis a vertical section of an article .of footwear made in accordance withthe present invention;

FIG. 2 is a perspective view of a rigid crush-resistant toe cap of thetype used in the practice of the invention. Toe caps of this type arewell-known articles of com- .merce in the footwear industry;

FIG. 3 is a sectional view of the toe cap after having been provided onboth sides with a layer of adhesive;

FIG. 6 is a perspective view of the complete toe-cap sub-assembly readyfor insertion into the toe portion of the article of footwear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The toe cap construction of thepresent invention is adaptable to provide toe protection for any kind offootwear whether it be a high boot, a boot of intermediate height or alow cut shoe such as an oxford. The toe cap comprises a rigid,crush-resistant toe cap provided with a lining consisting of a laminateof soft, resilient, compressible cellular elastomeric polymeric layerbonded to the toe cap and a stretchable fabric which is smooth intexture and has a low coefficient of friction bonded to the inner faceof the cellular elastomeric cushioning layer in any suitable manner. Thelaminate of cellular elastomeric polymeric material and stretchablefabric is adhered to the inside of a toe cap, which typically is made ofsteel, in such a way that the smooth stretchable fabric on one side ofthe foam is exposed to the foot. This adhesion is typically achieved bymeans of a layer of solvent-based thermoplastic adhesive applied to theinterior of the toe cap and allowed to dry by evaporation of solvent toa very tacky condition prior to application of the laminate. The outsidesurface of the toe cap is also provided with a layer of driedsolvent-based thermoplastic adhesive preferably in the same operation asthat wherein the inside adhesive layer is formed on the toe cap.

The toe-cap lining sub-assembly is placed directly into an otherwisefinished footwear article under conditions such that adhesion of theexterior of the toe cap to the interior of the upper of the toe portionof the footwear is achieved by reason of the adhesive layer on theoutside of the toe cap. The smooth interior fabric is preferably a nylontricot of well-known type in the textile industry. It providesprotection against chafing of the foot and also facilitates donning anddoffing. The cellular elastomeric layer provides excellent cushioningand thermal insulation. I

In one embodiment, the present invention is utilized in conjunction witha slush cast polyvinyl chloride (PVC) footwear process wherein thefinally fused article of footwear is made in a footwear-shaped mold inaccordance with the well-known slush casting or molding procedure suchas is described for example in U.S. patent to Streed et al. U.S. Pat.No. 2,974,373 dated Mar. 14, 1961. In this embodiment a plastisol isslush cast in a footwear-shaped mold, the mold is heated to fuse theplastisol in the mold and convert it to solid form, and the hot footweararticle is then stripped from the hot mold. The safety toe cap andlining assembly is separately fabricated by applying a coating of asolventbased thermoplastic adhesive to both the inner and the outerfaces thereof as by immersion in the solventadhesive solution removingthe toe cap from the adhesive solution, allowing the layers of adhesiveto dry by evaporation of solvent until they are very tacky and no longertruly wet, covering the inner face of the toe cap with a lining in theform of a laminate comprising the aforementioned cushioning layer ofcellular cured elastomeric polymeric material and a liner of thestretchable fabric covering bonded to the inner surface of thecushioning layer, with the other surface of the cushioning layer incontact with the adhesive layer on the inner face of the toe cap,thereby causing bonding of the laminate to the toe cap as a result oftackiness of the adhesive on the inside of the toe cap, and theninserting the resulting toe cap and lining assembly into the toe regionof the hot footwear article stripped from the hot mold and causingbonding of the toe cap and lining assembly to the footwear article as aresult of tackiness of the adhesive on. the outer surface of the toecap. Where available, residual heat in the footwear article may be usedto expedite the bonding of the toe cap to the footwear article.

Now referring to the accompanying drawings, a toe cap 1, such as a steeltoe cap of the type available commercially, as shown in FIG. 2 isemployed. Toe cap 1 is coated on both sides with an adhesive layer, asby dipping the toe cap in a container of solvent-based thermoplasticadhesive such as a thermoplastic polyurethane, for example any of manysuch adhesives available on the market. The resulting toe cap is shownin FIG. 3 as having a coating 2 of adhesive on the outside and a coating3 of adhesive on its inner face. This coated toe cap is allowed topartially dry to a tacky state and is then employed in both the assemblyof the toe cap and liner assembly and in the fabrication of the finishedarticle of footwear.

A laminate of the cured cellular cushioning material and the nylontricot fabric bonded together in any suitable manner, for example withan adhesive, and of a type commonly available commercially, is die cutto form a piece 4 (FIGS. 4 and 5) of the proper shape to conform to theinside of toe cap 1. Notch 4a is provided in die cut piece 4 in order toobtain perfect conformity of piece 4 with toe cap 1. Piece 4 is shown ashaving a cushioning foam layer 5 faced with nylon tricot liner 6. Thedie cut laminate piece 4 is then inserted into the adhesively coatedtoecap of FIG. 3 with the result that the piece 4 is firmly bonded to theinside of metal toe cap 1 as a result of the tacky adhesive layer 3. Theresult of this operation is the finished toe cap and lining assembly 7shown in FIG. 6.

The toe cap assembly 7 having the tacky outer adhesive layer 2 is theninserted firmly into the toe portion of the still hot footwear article8. The residualheat in the footwear article and the heat conducted intothe metal toe cap 1 of the assembly from the footwear article combine toactivate both adhesive coatings 2 and 3 and cause firm adhesion of thetoe cap and lining assembly 7 in permanent position in the article offootwear after the entire assembly is allowed to cool. The result is thearticle of footwear 9 portrayed in FIG. 1.

The greatest advantage of the present invention is the manner in whichit achieves the protective toe cap construction in the footwear article.The invention involves the complete pre-assembly of the toe cap andlining assembly externally with respect to the production of the articleof footwear itself. As a matter of fact, fabrication of the articles offootwear and of the toe cap and lining assemblies would typicallyproceed simultaneously in mass production manufacture in accordance withthe invention.

The technique of external prefabrication of the toe cap and liningassembly in accordance with the present invention greatly simplifies themanufacture of safety toe footwear by significantly reducing the numberof steps and complexity of assembly normally required in conventionalmethods of making safety footwear. ln addition, in practicing thepresent invention the toe cap is not encased within plies of fabricand/or rubbers as in all other commercially used safety toe footwearconstructions that the present inventor has seen. It is understood thatthe reason for this is that nonencapsulated constructions have notperformed satisfactorily prior to the present invention. As a-matter offact design experts associated with the present inventor did not feelthat the mode of construction of the instant invention would besuccessful. However the performance of applicants technique and of theresulting footwear has been exceedingly satsifactory to the greatsurprise of all concerned.

It is believed that the present invention is the first that accomplishesinsertion of a complete toe cap and lining assembly into an essentiallyfinished footwear article of any type such as for example a moldedfootwear article or a machine-made shoe, in a manner that is so GENERALThe invention is not limited to the use of metal toe caps but isapplicable with toe caps made of any other suitable material whichprovides the necessary crushresistance and impact-resistance. Examplesof other types of toe caps which can be used arethose made from hardrubber, rigid ABS (acrylonitrile-butadienestyrene) resins, rigid PVC,glass fiber-reinforced polyester resins, and vulcanized fiber.

The invention is not limited to slush cast footwear but can be appliedwith any other type of footwear such as injected PVC footwear,compression-molded rubber footwear or conventionally made footwear.

The cushioning layer 4 can be made of any suitable cellular polymericmaterial which provides the necessary give and comfort to the wearer.While an opencelled material can be used, a closed cell material can beused. Cellular material having both an open-celled (intercommunicatingcells) and a closed cell (notintercommunicating cells) structure canalso be used. Layer 4 can be sponge rubber, if desired.

Laminates of cushioning cellular material 5 and lining fabric 6 suitablefor use in the practice of the invention are available on the market.The fabric lining layer and the cellular layer of such laminates arebonded together in a manner known to the art. Instead of using apreformed laminate, in the practice ofthe invention fabric could bebonded to cellular polymeric material by use of a suitable adhesive, forexample.

The polyurethane foam preferably used for cushioning layer 5 has acompression-deflection value of about 1.4 pounds per square inch at 25percent deflection; a density of approximately 4 pounds per cubic foot,and a thickness of from one thirty-second to three thirtyseconds of aninch.

The preferred adhesive employed for forming adhesive layers 3 and 2,respectively bonding the cushioning layer 5 to the interior of the toecap 1 and the toe cap to the interior of the toe portion of the footweararticle, is a thermoplastic polyurethane polymer, for example Estane5713 (trademark) available from the HF. Goodrich Company, dissolved in asolvent consisting of tetrahydrofuran and methyl ethyl ketone insuitable relative proportions. The total solids content of the resultingadhesive solution can vary widely but for dipping application preferablyis approximately 25 percent by weight.

The invention is not limited to use of solvent-based thermoplasticadhesives for achieving bonding of the cushioning layer 5 to the toe cap1 and bonding of the toe cap 1 to the interior of the upper of thefootwear article 8, although such adhesives are most highly preferred.Any other suitable type of adhesive could be used in the practice of theinvention, for example hot molten adhesive although their use wouldintroduce certain complications.

Instead of using an immersion technique for applying adhesion layers 2and 3 to the toe cap 1, other methods of application such as brushing,spraying, fluidized coating, etc., can be employed.

If desired, especially where a metal toe cap 1 is used, the toe capcould be pre-heated prior to application of adhesive layers 2 and 3thereto and the residual heat in the toe cap 1 after such applicationcould be utilized to expedite bonding of cushioning layer 5 of laminate4 thereto and residual heat in toe cap 1' after such bonding could beutilized to expedite bonding of the toe cap to the inside face of theupper of the toe portion of the footwear article. However, suchpre-heating of toe cap 1 is not required to get good adhesion on bothsides thereof when a solvent-activated adhesive is used as describedabove.

It is preferred to carry out the present invention in such a way thatthe toe cap and lining is inserted in the footwear article while thelatter is at an elevated temperature of say from l25 to 225F. If thefootwear article is at. room temperature after manufacture, it ispreferred to pre-heat it so that it is at a temperature of l25-225F.when the sub-assembly of toe cap and lining is inserted therein.

The insertion of toe cap assembly 7 into the toe portion of the footweararticle 8 can be performed either manually or by machinery. Methods ofeffecting placement of assembly 7 in the toe portion will be readilyapparent to those skilled in the art.

While the foregoing describes the preferred embodiments of the instantinvention, it will be understood by those skilled in the art that manyvariations can be made therein without departing from the invention andthe spirit thereof. For example bonding of the toe cap to the upper ofthe footwear article can be carried out other than by conducting heatderived from the residual heat in the footwear article in the particularmanner described above. For example a metal toe cap and lining assembly7 could be inserted into the toe of the footwear article after whichheating of the metal toe cap could be carried out by induction heatingor by microwave means to achieve bonding to the upper of the toe of thefootwear. Less desirably a heater could be inserted within thesubassembly 7 after insertion of the latter into the boot. Similarly,alternate means of bonding the toe cap 1 to the foam side of die-cutlaminate piece 4 could be employed. Numerous other modifications andchanges which can be made without departing from the spirit of theinvention will be obvious to those skilled in the art.

I claim:

1. As an article of manufacture, a safety toe cap and lining assemblyadapted to be incorporated in an aticle of footwear during manufacturethereof, said assembly comprising a rigid toe cap, a coating of adhesiveon the outer surface of said cap, a cushioning layer of cellular curedelastomeric polymeric material covering and being bonded to the innersurface of said toe cap. and a liner of stretchable fabric having a lowcoefficient of friction covering and being bonded to the inner surfaceof said cushioning layer.

2. An article of manufacture as set forth in claim 1 wherein saidcellular cured elastomeric polymeric material is a polyurethane.

3. An article of manufacture as set forth in claim 2 wherein saidadhesive is a solvent-based thermoplastic polyurethane.

4. An article of manufacture as set forth in claim 1 wherein saidstretchable fabric is a nylon tricot.

5. An article of safety footwear comprising a footwear article, a rigidtoe cap located in the toe region of said footwear article and havingits outer surface bonded to the interior of the upper of said footweararticle in the toe region thereof, a cushioning layer of cellular curedelastomeric polymeric material covering and being bonded to the innersurface of said toe cap, and a liner of stretchable fabric having a lowcoefficient of friction covering and being bonded to the inner surfaceof said cushioning layer.

6. An article of safety footwear as set forth in claim 5 wherein saidcellular cured elastomeric polymeric material is a polyurethane.

7. An article of safety footwear as set forth in claim 6 wherein saidtoe cap is bonded to the interior of said upper by a thermoplasticpolyurethane adhesive and wherein said cushioning layer is bonded to theinner surface of said toe cap by a thermoplastic polyurethane adhesive.

8. An article of safety footwear as set forth in claim 5 wherein saidstretchable fabric is a nylon tricot.

9. An article of safety footwear comprising a slush cast footweararticle made of a fused plastisol, a rigid toe cap located in the toeregionof said footwear article and having its outer surface bonded tothe interior of the upper of said footwear article in the toe regionthereof, a cushioning layer of cellular cured elastomeric polymericmaterial covering and being bonded to the inner surface of said toe cap,and a liner of stretchable fabric having a low coefficient of frictioncovering and being bonded to the inner surface of said cushioning layer.

10. An article of safety footwear as set forth in claim 9 wherein saidcellular cured elastomeric polymeric material is a polyurethane.

l 1. An article of safety footwear as set forth in claim 10 wherein saidtoe cap is bonded to the interior of said upper by a thermoplasticpolyurethane adhesive and wherein said cushioning layer is bonded to theinner surface of said toe cap by a thermoplastic polyurethane adhesive.

12. An article of safety footwear as set forth in claim 9 wherein saidstretchable fabric is a nylon tricot.

2. An article of manufacture as set forth in claim 1 wherein saidcellular cured elastomeric polymeric material is a polyurethane.
 3. Anarticle of manufacture as set forth in claim 2 wherein said adhesive isa solvent-based thermoplastic polyurethane.
 4. An article of manufactureas set forth in claim 1 wherein said stretchable fabric is a nylontricot.
 5. An article of safety footwear comprising a footwear article,a rigid toe cap located in the toe region of said footwear article andhaving its outer surface bonded to the interior of the upper of saidfootwear article in the toe region thereof, a cushioning layer ofcellular cured elastomeric polymeric material covering and being bondedto the inner surface of said toe cap, and a liner of stretchable fabrichaving a low coefficient of friction covering and being bonded to theinner surface of said cushioning layer.
 6. An article of safety footwearas set forth in claim 5 wherein said cellular cured elastomericpolymeric material is a polyurethane.
 7. An article of safety footwearas set forth in claim 6 wherein said toe cap is bonded to the interiorof said upper by a thermoplastic polyurethane adhesive and wherein saidcushioning layer is bonded to the inner surface of said toe cap by athermoplastic polyurethane adhesive.
 8. An article of safety footwear asset forth in claim 5 wherein said stretchable fabric is a nylon tricot.9. An article of safety footwear comprising a slush cast footweararticle made of a fused plastisol, a rigid toe cap located in the toeregionof said footwear article and having its outer surface bonded tothe interior of the upper of said footwear article in the toe regionthereof, a cushioning layer of cellular cured elastomeric polymericmaterial covering and being bonded to the inner surface of said toe cap,and a liner of stretchable fabric having a low coefficient of frictioncovEring and being bonded to the inner surface of said cushioning layer.10. An article of safety footwear as set forth in claim 9 wherein saidcellular cured elastomeric polymeric material is a polyurethane.
 11. Anarticle of safety footwear as set forth in claim 10 wherein said toe capis bonded to the interior of said upper by a thermoplastic polyurethaneadhesive and wherein said cushioning layer is bonded to the innersurface of said toe cap by a thermoplastic polyurethane adhesive.
 12. Anarticle of safety footwear as set forth in claim 9 wherein saidstretchable fabric is a nylon tricot.